What does the “uw” mean at the beginning of variable names in STM32 examples?

问题

As I read STM32 example code I see a fair number of variables that begin with uw. Ex:

static __IO uint32_t uwLsiFreq = 0;
__IO uint32_t uwCaptureNumber = 0;
__IO uint32_t uwPeriodValue = 0;
__IO uint32_t uwMeasurementDone = 0;

Everything has a meaning or a story behind it. What does uw mean here?

Example Source: STM32Cube_FW_F2_V1.7.0/Projects/STM32F207ZG-Nucleo/Examples/IWDG/IWDG_Example/Src/main.c.
Download link --> click "Get Software" button next to "STM32CubeF2".

回答1:

Alright, I'd like to post my own, more complete answer. Thanks to @njuffa for pointing out in a comment below my questions that "Probably: uw stands for 'unsigned word' in some sort of Hungarian notation," thanks to @PeterJ_01 for pointing out that the CEO of Stack Overflow has some opinions on the matter, and thanks to @Sigve Kolbeinson for pointing out in a comment under PeterJ_01's answer that the CEO of Stack Overflow's name is Joel Spolsky (as found in the link), he actually doesn't hate Hungarian notation, but rather is just upset a limited and corrupted form of it [Systems Hungarian] got traction for a while, and for giving us the actual link to the article so we can learn more and read the article ourselves.

1. Here's my conclusion to answer my question:

uw at the beginning of many STM32 example variables certainly must logically mean "unsigned word," where a "word" is 32 bits in this case. Knowing this adds a lot of clarity as I read the code, and removes some confusion about the names, so I'm glad to know this.

In this case, this is a type of Systems Hungarian usage, which is frequently discouraged for languages which have explicit types, such as C and C++, since it's redundant and adds little value. Contrast this to Apps Hungarian, which I describe below, which Joel Spolsky (CEO of Stack Overflow) strongly promotes as a way to help make "wrong code look wrong."

2. Here's some additional insight (primarily about Hungarian Notation) I learned along the way from @Sigve and @njuffa via their comments and the links they provided:

You might just call this section "what exactly is Hungarian notation in computer programming?"

1. Hungarian notation exists (I didn't know about it before), and refers to the concept of adding a few extra characters at the beginning of each variable and/or function name to provide additional information about the variable or function, such as its purpose, its type, or its return type.
2. Inadvertently this answered my question about FreeRTOS naming conventions too. Now I know! They use [primarily Systems] Hungarian notation as well. Here's some links. Note that in the first link you'll see a list of all of the Hungarian notation usages in FreeRTOS. This notation is almost entirely Systems Hungarian notation, but arguably uses a little bit of Apps Hungarian notation too when they specify the name of the file in which functions and macros are defined right inside the function or macro name.
   • FreeRTOS Hungarian Notation
   • what is v and x means in freeRTOS task creating or used in it?
   • https://www.freertos.org/FreeRTOS-Coding-Standard-and-Style-Guide.html#NamingConventions
3. Hungarian notation has two main forms: Systems Hungarian and Apps Hungarian. See their differences here.
   • Systems Hungarian is essentially a corruption of the original intent of "Hungarian" notation that came about when it's creator, Charles Simonyi's, mistakenly used the word "type" instead of "kind" in his description of it (source). Charle's original intent was to encode additional information into variable names that isn't inherent in the programming language itself. However, Systems Hungarian notation says basically to store the variable's type into the variable name. Ex: unsigned long myVar now becomes unsigned long ulMyVar. Most people seem to argue this is either of limited use or completely worthless. Joel Spolksy is not a proponent of this form of Hungarian notation, as indicated in his article, but he is strongly for Apps Hungarian style. Other opinions can be found in the "Notable opinions" section of the Wikipedia article here.
   • Apps Hungarian describes the concept of storing additional information into the front of a variable name which can NOT otherwise be easily deduced, such as using us to mean "unsafe string" and s to mean "safe string". Many people either feel more neutral towards this method, or like it and promote it. Both Joel Spolsky (CEO of Stack Overflow) and Steve McConnel think it's a good idea and promote its usage.

Note, here's a useful excerpt from Joel's article:

Somebody, somewhere, read Simonyi’s paper, where he used the word “type,” and thought he meant type, like class, like in a type system, like the type checking that the compiler does. He did not. He explained very carefully exactly what he meant by the word “type,” but it didn’t help. The damage was done.

Apps Hungarian had very useful, meaningful prefixes like “ix” to mean an index into an array, “c” to mean a count, “d” to mean the difference between two numbers (for example “dx” meant “width”), and so forth.

Systems Hungarian had far less useful prefixes like “l” for long and “ul” for “unsigned long” and “dw” for double word, which is, actually, uh, an unsigned long. In Systems Hungarian, the only thing that the prefix told you was the actual data type of the variable.

This was a subtle but complete misunderstanding of Simonyi’s intention and practice...

(emphasis added)

回答2:

It means unsigned word in this naming convention. Almost not used now. But some people love it as it shows them what type the variable is. Another ones hate arguing that it is one of the worst programming habits (including the creator of the Stack Overflow ). IMO it does not matter

来源：https://stackoverflow.com/questions/50072074/what-does-the-uw-mean-at-the-beginning-of-variable-names-in-stm32-examples